Current studies are directed to the biological features of mycoplasmas associated with human respiratory and urogenital infections and those organisms recovered from various human tissues. Specifically, we want to assess their ability to stimulate antibody responses in various hosts (including man), to understand properties of the organisms that allow one to identify and distinguish individual members (i.e. different species) occurring in a variety of hosts, and composition and nature of outer membrane components on the organisms that promotes their ability to adhere to human and other tissue cells, and to initiate disease. We also are concerned with the genetic and biologic properties of mollicutes, and how this information may contribute to a better understanding of how these smallest of biologic entities sustain self-replication.